Electric furnace.



P; BU NET.

' ELECT APPLICATION RIL FYURNACEp -F|LED NOV. 24, I814.

Patented Jul 6, 1915. 2 SHEETS-SHEET 1'.

- wwhm P BUNE'T.

ELECTRIC FURNACE.

1 N FILED NOV 24 194' APPLIC 1 1; 11 1:5348. Patented July 6;1915mum's-spin 2.

UNITED STATES PAUL ome, or WHITNEY, NORTH mm, 'AssIGu'oR To soomrr':.GEHERALE Dnsi NITRURES, OF PARIS, FRANCE.

EL'nornIc rummcn,

i Specification of Letters Patent.-

. j.- -i q1:app lieation fi led m 9,- 1 913, Seria1 Nb. 766,461..Divided and this application filed November 24,

To all it may concern:

Be it known thatI, PAUL'B NEnpf Whitney, Stanly county, North Carolina,and a I vcitizenof the Republic of-France, have invented certain new anduseful Improvements, iii-Electric Furnaces, of which the followingis'aspecification. I

4 This invention relates to'a revolving electric furnace, moreparticularly adapted. to carry out a process for. the manufacture ofaluminium nitrid by the methodcwhich con- 'sists in heating-in presenceof nitrogen or of gases containing the latter, amixture of alumina oraluminous substances and carhon 1n electrical reslstance furnace inwhich thematerial under treatment ltself serves as the heating resistancMy IHVGIIl ZiOII COIISi StS in the construction? v of the continuouselectrical furnace'so as to above substances containing an excess ofvcarbon or other conductivesubstances in sufficientquantity to insure thepassage of ourrent-in'spite of the reactionary losses ofcaralumina intoaluminium nitrid.

effect the advance of the mixture of the bon ,'necessaryfto thetransformation of the 7 My invention. may be embodied in fur- .naces ofdiiferent types, such as hereinafter described. ,The first type offurnace is arranged in such a waythat the thickness of the layer ofmaterial goes on increasing in proportion as the latter advances throughI 1 the furnace. In this'way the sectional area increases in the partsof the'furnace Where the mixture becomes poor in carbon inconsequence ofthe reactlon, andthere 1s, therefore, always at -ever y cross-section ofthe furnace a-suflic1entquant1tyof conductive 1 material to insure theregular passage of the current. The second type of furnace is a soarranged that at intervals along its length thereg .are connectionsor'electrodes for conveying the current, which are connected alternatelyto the two poles of the generator or supply. divided into In this waythe I furnace is a number of elements or sections through which thematerial under treatment: passes successively; the'length of eachsection can be selected in accordance with the state of conductivity ofthe material treated therein. These two types of furnace can evidentlybe combined.

21912., "The gas direction to the 'm'atenal 1914. Serial N0.873,781'.

The accomp ny-il furnaces for carrying out the process. lgure 1 1s alongitudinal section, .illus-fl' trating'anr inclined revolving.electric fink;

" PatentedJuly6,1915 j 1 nace, acco'rding'to my invention Fig.1 2 is a I(vertical section" of a'istationary form' of-fur- 'nace;rF1g's. 3 and}are diagrammatic sec-f fied forms' of revolvingtions of'two" d electricfurnaces Fig-ll shows a revolving'furnace which is slightly inclined soto allow the-substances introduced; into "the furnace to ad,

" nte h f th QtIglimin a continuous manner, after the-general," methdddescribed in the Serpek Pat ontainmg nitrorent is led to two annulconductors A and B of which the lower (in-e Theielectric curiprojectsins'ide the furnace so asto form a diaphragm and to retain thematerial C traveling through the furnace. Asezgplained abovei inproportion as the materialadvances through the furnace and' thetransformation into-.nitridbecomes very complete, the thiclmes'sfo'fthelayer is 'increased in; this way'allowing of maintaining at everycross-section the quantity of carbon sufiicient to insure theregularpassage of the current inspite of the losses resulting from. thereaction; Matters can, therefore, be so arranged that the resistance,

'the furnace and to facilitate the passage of the current at the start,the operation may be commenced by passing carbon alone and consequentlythe evolution of heat are I through the furnace; the mixture to betreated is then gradually'added. There may be arranged in the furnace atcertain intervals conductive rings D fitted in the refractory lining, E,and projecting ornot. In

this way there are formed in the furnace zonesofless resistance whichfacilitate the I passagefof the current. This arrangement allows thefurnace to be madefof'any length,

jection of the conductive rings D.

greater in proportion to the size of the pro- I Fig. 2 of the drawingshows a stationary furnace based upon the same prmclple; the

I trode B The electrode A is insulated on its underside by an insulatingsupport A in furnace is vertical and the current is led to the twoelectrodes A and B The material poured upon the side of the electrode Afalls upon the lateral walls of the furnace forming a sloping bank, thesectional area of which increases toward the lower eleccreasing ordecreasingthe separation of the the mixture.

electrodes and the areas for the passage of Openings F, closed by plugsF are formed at the bottom of the furnace at various points in theperiphery to allow the material to be withdrawn. 1

Fig.3 is a longitudinal section of a furnace of the second type, inwhich an intermediate electrode or terminal B is arranged between theextreme electrodes A A, all

- these electrodes being formed as conductive rings or annuli. Fig. flis a longitudinal section of a similar furnace, having two intermediateelectrodes; in this case some of the conductive rings forming terminalshave been'arranged to project internally of the furnace so as to affordwalls or diaphragms according to the principle of the first type offurnace above described. In the arrangement of Fig. 4, the conductiverings A, .A are connected to one of the-poles of the-electricalgenerator while the alternate rin s B B* are connected to the otherpole. n

these-two figures, E still indicates the refractory lining. of thefurnace and The current of nitrogen circulates in the opposite'directionas usual.

The use of intermediate electrodes and the possibility of selectingtheir separation as desired, form a practical method which al- 1 lowslatitude for regulating in accordance tion of the furnace, proportion ofthe con-' ductive material added to the mass in reaction, totalexpenditure of energy and of heat and division of the matter along thevarious elementary sections of the furnace In par-" ticular, by reducingthe length of the path traveled by the material between two successiveelectrodes, the resistance is diminished. It becomes possible,-therefore, to reduce the quantity of conducting material added to thematerials in reaction in order to insure the passage of the current;this allows of diminishing the expenditure of ener devoted to theheating of these conductlve materials and to obtain at the end Theelectrode A and its support A the ma-. terial in course of its advancetherethrough.-

of the operation a product which is not surcharged with inert materialand is, thereforeyricher in nitridi.

Instead of reducing the proportion of conductive matter added, thelength of the furnace may be increased without reaching. aresistancedeleterious to the satisfactory carrying out of the operation. In thisway there is obtained a result analogous to that whichis produced bytheconductive rings D, 'which are not connected tothe poles of thegenerator in the furnace shownin Fig. 1. Again, by bringing closertogether-two consecutive electrodes, the heat may be concentrated in'agiven zone as desired, for example in the final zone which is thepoorest in carbon'and. in whichthe current has most difiiculty inpassing.

Another peculiarity of the type of furmice, which presents an importantpractical advantage, lies inthe fact that itrealizes au-' tomaticallythe regulation of the intensity of the current, and, therefore, of thequantity of heat which passes through the different elementary sectionsof the furnace. Indeed, if for any reason the intensity of thec'urrentincreased abnormally at one of the sections of the furnace, to thedetriment of the others, there would be produced at that point a largerquantity of heat; this would increase the reaction of the carbon andalumina. There would result an elimination of carbon in the state ofcarbon monoxid and the reacting mixture would become less conductive;this would cause a reduction in the intensity of the current in thissection and so reestablish the general equilibrium.

As has been said before, it is advanta geous to combine the useofintermediate electrodes with the system of furnace-diaphragms as shownin Fig. 1; such an arrangement is illustrated in Fig. 4. In this way itbecomes possible to combine the useful effects of the methods ofregulation of the two systems, according to different requirements; Inparticular, it becomes possible to vary as desired in each elementarysection of the furnace, the thickness of the layer ofmaterial undertreatment, and'the extent which it occupies between the consecutiveelectrodes.

As stated above, the material delivered to the furnace may be a mixtureof alumina and carbon with an excess of the latter over or above thequantity necessary to the reaction. By way of example, it may be statedthat there may be introduced into the mixture a quantity of carbondouble that which -is necessary to the reaction. A part. or the whole ofthis excess of carbon may, however, equally well be replaced by one ormore substances which are good electrical conductors, the metals forexample. Among these substances, it is of advantage to select thosewhich possess at the same time the 5. lower crown projecting internallyo furnace,in such a way as' to increase the thickness of the layer ofmaterial treated toward the outlet end.- I i property of actifying thereaction of forma- I nace having conductiverings and means for,supplying current thereto and intermediate tionof 'niti'id. ,One may,for -example, use 1ron, copper,fn1ckel, manganese of then: ores "oragain alloys .of, these metals, such as.

5 ferro-nickel, ferro-s'ilicon, ferro-manganese,

etc. The-use of iron or of certain of its alloyshas the further.-special advantage of allowin it to be se arated eticall from the-aluminum n'i trid at tli bi d of thz 5 operation. Since iron oxidisalready'foundin greater or less proportions in certain aluminium ores,(in particular the ferrm,

ginous bauxites, for example), it fwill be sufficient in case oftheuseof these ores to" complete by additions the quantity of iron,

requiredto obtain the desired conductivity of the mass under treatment."I he material introduced into the furnace" whatever be its compositionand whatever a the type of furnace employedfmay. be in the pulverulent"state or. in thezform jof agglomerates; it may again be in'the form'or'agglomerates containing onlyvthe alumina or aluminous .material'andthe carbonnecessary to the reaction, whilethe carbon or other conductivematerial intended'to insure the desired conductivit'} .is addedseparately. In case'the conductivematerial' added consists Wholly orin-parttgof carbon, the atmospheric air 3. may be useddirectly as thegas of the reac- 'tion; the excess of carbon contained in the materialmay then serve .at the end of the voperationf andbeyond theelectrical=zone to deprivethia air of its oxygen.

66,461, the present application being a divi "J sion offsaid' priorapplication.

nace, having two conductlve crowns, and

means for I supplying current theretot the the i source, to, divide thei g I for the rings."

, Theprocesses which I have above de-'. -1 scribed as capable'of beingcarried out. in my I furnaces, form the subject of a separate ap-'licationfiled by me Mayj9, 1913, Serial No.'

conductive rin s interposed at difi'erent :points in there ractorywallofthe furnace.

3'. An inclined revolving' electrical furnace in the length ofwhich arearranged electrodes which are connected alternately to eachv of the twoipioles of a generating of elementary sections, the length of each ofwhich can'be selected. according to the state conductivity possessed bythe material at the time of passing this-section.

rnace into a'number :4. A, slightly inclined revolvingcontinuopsfiirnac'e, having electrodes spaced along th'el'ength of thefurnace, and in which the separatlon of the-electrodes diminishes in thedirection of'the advance of the material,

'that is .to-say, according as the latter be-- comes less conductiveasthe reactions go on.

5. An inclined revolving electric furnace having ,jelectr'odes in theform of diaphragms with decreasing orifices for the pas,- sage of thematerial, to vary the-thickness of the layer of material under treatmentand the extent whichit occupies between the electrodes. t

6. In an inclined rotary electric furnace, a lining composed ofrefractory conducting rings and refractory nonconducting' materialbetween the rings to insulate thesame from each other; and electricalconnections 7 V -7.- In an inclined'rotary electric furnace,

a lining composed of carbon ringsand re- ,f ractory non-conductingmaterial between the carbon rings to insulate the same from each other;a conductive char e bridging the rings and electrical connectlons forthe rings. j

.In testimony whereof I have signed my name to this specification twosubscribing witnesses.

.Witnesses: y I W. F. ROCKWELL, W. P. MARs'nnmns.

PAUL BUNET.

in the presence of. 1

